The present invention relates to packaging machines for containers, such as cartons for containing milk, and, more particularly, to packaging machines including a bottom breaker.
Packaging machines of the type mentioned are already known for use with tubular containers of square to rectangular cross section. The containers each have a bottom forming portion comprising first to fourth bottom panels continuous with one another, the first bottom panel having a pair of cuts formed in the center of the outer end thereof to provide a fold forming portion between these cuts for preventing a liquid from permeating the end. The packaging machine comprises a rotor having radial mandrels and intermittently drivable so as to stop each of the mandrels at first and second process stations in succession, the container being fitted around the mandrel with the bottom forming portion projecting therefrom and with the first bottom panel facing to the right, a bottom breaker for prefolding the bottom forming portion of the container as fitted around the mandrel stopped at the first station so as to render the bottom forming portion foldable flat and for prefolding the fold forming portion by bending the fold forming portion rightward along a base part thereof, a folding rail for guiding the prefolded bottom forming portion of the container fitted around the mandrel from the first station to the second station during the movement of the mandrel from the first to the second station while folding the bottom forming portion flat by contact therewith, and a bottom press for folding flat and bonding under pressure the bottom forming portion of the container fitted around the mandrel as stopped at the second station. The folding rail comprises right and left two rail members, with a clearance formed therebetween for permitting the outer end of the prefolded bottom forming portion of the container fitted around the mandrel to be inserted thereinto during the movement from the first to the second station.
The packaging machine described above has the problem that while the bottom forming portion moves along the folding rail, the prefolded fold forming portion restores itself to the original state owing to the property of the container material to spring back, with the result that the bottom forming portion including the fold forming portion can not be folded satisfactorily to the specified shape.
An object of the present invention is to provide a packaging machine which is adapted to prevent the prefolded fold forming portion from restoring itself owing to the springing-back property of the container material.
The present invention provides a packaging machine for tubular containers of square to rectangular cross section, each of the containers having a bottom forming portion comprising first to fourth bottom panels continuous with one another, the first bottom panel being formed with a fold forming portion in a center of an outer end thereof for preventing a liquid from permeating the end, the packaging machine comprising: a movable body having mandrels and intermittently drivable so as to stop each of the mandrels at first and second process stations in succession, the container being fitted around the mandrel with the bottom forming portion projecting therefrom and with the first bottom panel facing to the right, a bottom breaker for prefolding the bottom forming portion of the container as fitted around the mandrel stopped at the first station so as to render the bottom forming portion foldable flat and for prefolding the fold forming portion by bending the fold forming portion rightward along a base part thereof, a folding rail for guiding the prefolded bottom forming portion of the container fitted around the mandrel from the first station to the second station during the movement of the mandrel from the first to the second station while folding the bottom forming portion flat by contact therewith, and a bottom press for folding flat and bonding under pressure the bottom forming portion of the container fitted around the mandrel as stopped at the second station, the folding rail comprising right and left two rail members with a clearance formed therebetween for permitting an outer end of the prefolded bottom forming portion of the container fitted around the mandrel to be inserted thereinto during the movement from the first to the second station. The packaging machine is characterized in that an unfolding preventing guide member is disposed in the rail clearance so as to come into contact with a required part of the bottom forming portion during movement through the clearance.
With the packaging machine of the present invention, the clearance between the two rail members has disposed therein an unfolding preventing guide member which comes into contact with the required part of the bottom forming portion during movement through the clearance, so that the guide member prevents the prefolded fold forming portion from restoring itself to the original state owing to the property of the container material to spring back.
The part of the bottom forming portion to be brought into contact with the guide member during the movement through the rail clearance is the left side of the base part of the fold forming portion. Even if the prefolded fold forming portion acts to fall down leftward for unfolding, this portion is then prevented from falling down by contact with the guide member, and is unlikely to unfold.
The folding rail starts to fold the prefolded bottom forming portion of the container fitted around the mandrel during the movement from the first to the second station upon the bottom forming portion coming into contact with the rail members, and the left side of the base part of the fold forming portion is brought into contact with the guide member after the bottom forming portion has moved a predetermined distance from the time of coming into contact with the rail members. Since the folding rail folds the bottom forming portion immediately after the guide member prevents the fold forming portion from falling down in this case, the guide member acts on the fold forming portion at the most suitable position.
When the guide member comprises a roller having a rotary shaft extending orthogonal to the direction of movement of the mandrel, the guide member is unlikely deface or damage the container.